Presence of ghost cells and the Wnt signaling pathway in odontomas

BACKGROUND: Although it has been reported that ghost cells are present in odontomas, the generation mechanism of these cells is unclear. To evaluate the presence of ghost cells and involvement of the Wnt signaling pathway, we examined the expression of hard keratins, beta-catenin and Lef-1 in odontomas. METHODS: Sixty-nine cases of odontoma were examined immunohistochemically with the use of antibodies against human hair proteins, beta-catenin and Lef-1. RESULTS: Expression of hard keratins was found only in the cytoplasm of ghost cells in 46 (66.7%) of the 69 odontomas. Compound odontomas (78.8%) showed a higher incidence of ghost cells than complex odontomas (29.4%). Histopathologically, ghost cells were found within odontogenic epithelium adjacent to immature enamel and in the centre of Liesegang-ring-like calcified materials. Expression of beta-catenin and Lef-1 was observed in the cytoplasm and nucleus of odontogenic epithelial cells adjacent to the ghost cells in immature odontomas. CONCLUSION: These findings suggest that odontoma is a hard keratin-expressing tumor-like lesion, and that the Wnt signaling pathway may be involved in the formation of ghost cells in odontomas.     

Establishment of mesenchymal cell line derived from human developing odontoma

Oral Diseases (2012) 18, 756-762 Objectives: An odontoma, which shows proliferating odontogenic epithelium and mesenchymal tissue, is one of the most common odontogenic tumors encountered. These are commonly found in tooth-bearing regions, although the etiology remains unknown. There are no previous reports of an established line of immortalized human odontoma cells. Methods: Using odontoma fragments obtained from a girl treated at our department, we established an immortalized human odontoma cell line and investigated cell morphology, dynamic proliferation, the presence of contamination, and karyotype. Moreover, cell characterization was examined using osteogenic and odontogenic markers. Results: We successfully established a mesenchymal odontoma cell (mOd cells). The cells were found to be fibroblastic and had a high level of telomerase activity. Cell growth was confirmed after more than 200 population doublings without significant growth retardation. mOd cells expressed mRNA for differentiation markers, including collagen type I (COLI), alkaline phosphatase, bone sialoprotein, osteopontin, osteocalcin, cementum-derived protein (CP-23), dentin sialophosphoprotein (DSPP), and distal-less homeobox 3 (DLX3), as well as bone morphogenetic proteins (BMPs). In addition, they showed a high level of calcified nodule formation activity in vitro. Conclusions: We successfully established a cell line that may be useful for investigating the mechanisms of normal odontogenesis as well as characteristics of odontoma tumors.     

A new osteopetrosis mutant mouse strain (ntl) with odontoma‐like proliferations and lack of tooth roots

A new spontaneous mouse mutant (ntl) with autosomal‐recessive osteopetrosis was characterized. These mice formed tartrate‐resistant acid phosphate (TRAP)‐positive osteoclasts but their osteoclasts had no ruffled border and did not resorb bone. These mice displayed no tooth eruption or tooth root formation. Adult mutant mice developed odontoma‐like proliferations near the proximal ends of the incisors. Intraperitoneal injection of progenitor cells from the liver of 16.5 days postcoitum wild‐type embryos into newborn mutants rescued the osteopetrosis phenotype, indicating that the defects were intrinsic to the osteoclasts. Our findings not only provide further support for a critical role of osteoclasts in tooth eruption and tooth root development, but also suggest that the perturbation of the homeostasis of the odontogenic precursors of the incisors is primarily responsible for the development of the odontoma‐like proliferations in this osteopetrosis mutant. Genetic mapping has narrowed down the location of the mutant allele to a genetic interval of 3.2 cM on mouse chromosome 17.     

Odontogenic tumors in Chile: a study of 362 cases.

BACKGROUND: Odontogenic tumors are infrequent lesions. Thus, the review of a large number of cases becomes a necessity for both the pathologist and the clinician. Studies on odontogenic tumors have been published in many parts of the world, but there is little information available in the English language literature on the relative frequency of odontogenic tumors in Latin America. The aim of this study was to determine the relative frequency of this heterogeneous group of lesions in a Chilean population, and to compare these data with previous reports. METHODS: We reviewed the records of 28,041 specimens from 1975 to 2000 in the Oral Pathology Referral Institute (IREPO), and using the criteria for histological typification published by the World Health Organization in 1992, we reclassified the odontogenic tumors. RESULTS: We confirmed a total of 362 odontogenic tumors. The frequency of odontogenic tumors as a percentage of all pathological specimens in our institute was 1.29%. The most frequent histological type was odontomas (44.7%), followed by ameloblastomas (20.4%) and myxomas (8.8%). CONCLUSIONS: Odontogenic tumors are uncommon lesions in the Chilean population and malignant odontogenic tumors are very rare. The relative frequency of various types of odontogenic tumors, as well as the age and gender distribution are similar to those reported in the North American series and different from those found in recently published Asian and African series.     

Ultrastructural features of the epithelial-mesenchymal interface in an ameloblastic fibro-odontoma

The ultrastructural features of the epithelial-mesenchymal interface in a case of an ameloblastic fibro-odontoma was studied with special reference to possible signs of “inductive” processes. In most parts of the tumor, the odontogenic epithelium was separated from the connective tissue by a thick rim of a finely filamentous mesh work in which a basal lamina was occasionally observed. Mesenchymal cells were seen to touch the filamentous mesh work but no membrane bound matrix vesicles were recorded. Small areas of dentin-like tissue were found in the juxtaepithelial connective tissue while enamel-like areas and spherical calcified masses were encountered in epithelial islands. The organic matrix in relation to the enamel-like tissue consisted of either tubular fibers or a fine-granular material. It was assumed that the tubular matrix component directed the formation of long enamel-like crystals, and that the fine-granular matrix was degraded tubular fibers in which spherical calcified masses might arise. Spherical calcified masses could be found in separate follicles also where they were related to a fine-fibrillar matrix or collagenous material. The cell layers forming the wall of the islands had a great resemblance to those of an enamel organ, but the findings of dentin-free, enamel-like areas are not compatible with the inductive theory of normal odontogenesis.     

Developmental anomaly of permanent teeth related to traumatic injury

Abstract A case is presented where a 4-year-old girl was injured in an automobile accident. The dental injury, intrusive luxation of the maxillary deciduous incisors, seemed unimportant at the time, since the child was in critical condition. The situation was first evaluated 5 years later, when the child was referred for treatment of an apical periodontitis originating from the right central incisor. The present case reflects several important aspects that were overlooked at the time of injury: the potential of intruded luxated deciduous teeth to cause developmental anomalies to the permanent dentition; the necessity of a longer follow-up period to detect such anomalies; and the need to develop effective treatment methods.     

Spontaneous ameloblastic fibro-odontomainafemalemouse

A spontaneous ameloblastic fibro-odontoma is described in a 73-wk-old female mouse. The tumor was located in the molar mandibular region. The diagnosis was made on the basis of the histologic presence of odontogenic epithelial tissue embedded in mesodermal tissue resembling dental papilla, and containing in addition dentin and enamel. The positive reaction for keratin and vimentin confirmed the presence of ectodermal and mesodermal elements respectively in the tumor.     

Disturbed tooth eruption in osteopetrotic (op/op) mice: histopathogenesis of tooth malformation and odontomas

BACKGROUND: Odontoma-like structures are formed in the jaw bone of osteopetrotic (op/op) mice, which have a congenital deficiency in osteoclastic differentiation due to the absence of functional macrophage colony-stimulating factor (M-CSF). METHODS: To clarify the histopathogenesis of tooth malformation and odontoma-like structures, a 2-year postnatal process of development of the op/op mandibular incisor was examined radiologically and histologically. At the same time, extracellular matrix (ECM) remodeling around tooth germs was analyzed immunohistochemically. RESULTS: Abnormal forms of op/op tooth germ were noticeable even at 3 days after birth on a radiogram. Histologically, op/op mice were clearly distinguished by the disappearance of dental follicular space at 3 days. With aging, bone trabeculae, which were not remodeled, penetrated into op/op tooth germs and divided them into several daughter germs, which were recognized as odontomas. In mandibular incisor bodies, the immature ECM components, such as heparan sulfate proteoglycan and tenascin, were preserved diffusely in the dental papilla/pulp, which indicates that maturation of the stroma does not take place in op/op mandibular incisors. CONCLUSION: The observation suggests that the disturbed morphogenesis of op/op tooth germs is functionally explained by the disordered immunolocalization of ECM molecules, and that the dental follicular space is essential for normal tooth development because it prevents bone penetration into the tooth germs.     

Compound composite odontoma with unusual number of denticles – A rare entity

Compound odontoma is stated to be a hamartomatous lesion rather than a true odontogenic tumour. It has an unknown etiology and often suspected when there are retained deciduous teeth in children. Early detection and surgical enucleation of the tumour is recommended to prevent impaction of unerupted teeth. In this index case, multiple denticles or rudimentary teeth, numbering 37 were enucleated from the maxillary anterior region of a 17-year old male, which makes this case unusual. Evidence of concrescence, fusion and dilaceration were observed in the denticles enucleated, the size of which varied from 4 mm to 12.5 mm.